Energy from ATP hydrolysis

Energy from ATP hydrolysis used to pump H out against electrochemical gradient... 

Substrate cycling (e.g. the Cori cycle and the intra- and inter-cellular triacylglycerol/fatty acid cycles (Chapter 3)) in which there is no net metabolic change so that the energy from ATP hydrolysis is released as heat. 

Replication starts by the separation of the strands of DNA and the formation of a local bubble at a specific DNA site called the origin of replication (ori). A helicase enzyme uses energy from ATP hydrolysis to effect this action. Single-strand DNA binding proteins stabilize the strands during the subsequent steps. The original DNA strands will function as the templates that will direct synthesis of the complementary strands. A nucleotide on the template strand will determine which deoxyribonucleotide (dNTP) will be incorporated in the newly synthesized strand. This replica-... 

Type I topoisomerases catalyze the relaxation of supercoiled DNA, a thermodynamically favorable process. Type II topoisomerases utilize free energy from ATP hydrolysis to add negative supercoils to DNA. The two types of enzymes have several common features, including the use of key tyrosine residues to form covalent links to the polynucleotide backbone that is transiently broken. 

A FIGURE 3-24 Structure of myosin II. (a) Myosin II is a dimeric protein composed of two identical heavy chains (white) and four light chains (blue and green). Each of the head domains transduces the energy from ATP hydrolysis into movement. Two light chains are associated with the neck domain of each heavy chain. The coiled-coil sequence of the tail domain organizes myosin II into a dimer, (b) Three-dimensional model of a single... 

Flellcases use energy from ATP hydrolysis to separate the parental (template) DNA strands. Primase synthesizes... 

The helicase activity of one of the TFIIH subunits uses energy from ATP hydrolysis to unwind the DNA duplex at the start site, allowing Pol II to form an open complex in which the DNA duplex surrounding the start site Is melted and the template strand Is bound at the polymerase active site. If the remaining ribonucleoside triphosphates are present, Pol II begins transcribing the template strand. As the... 

Energy from ATP hydrolysis drives many nonspontaneous cell reactions ... 

Muscle converts chemical free energy from ATP hydrolysis into mechanical work with an efficiency approaching 80% under optimal circumstances. ATP is only an intermediary in energy storage in red muscles. Its concentration remains relatively constant during long exercise, as shown in the NMR studies of Figure 12,14. 

The primary step in the urea cycle is the synthesis of carbamyl phosphate from ammonia and carbon dioxide (11.76). This first stage, and the later stage of synthesis of arginosuccinic acid from citrulline and aspartic acid, both require the transfer of energy from ATP hydrolysis. The pyrophosphate formed in the latter reaction is itself hydrolysed which, together with the former reaction. 

However, in the Born-Haber process, the commercial production of ammonia, the formation of the partially reduced intermediates requires high temperature and pressure. Remarkably, by acquiring energy from ATP hydrolysis and coupling the reaction with hydrogen (H2) formation,... 

Kitamura, et al. (103) found single mechanical steps of 5.3 nm with two to five such steps in rapid succession for myosin. Only one ATP is consumed. Most interestingly, their results indicate that the myosin head may be able to store energy from ATP hydrolysis, and release it later in several packets of productive work. 

Every time we contract muscles, move substances across cellnlar membranes, send nerve signals, or synthesize an enzyme, we nse energy from ATP hydrolysis. In a cell that is doing work (anabolic processes), 1 to 2 million ATP molecnles may be hydrolyzed in one second. The amonnt of ATP hydrolyzed in one day can be as much as our body mass, even though only abont 1 g of ATP is present in our cells at any given time. 

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